The present invention relates to a keyboard assembly, and more particularly to a novel construction of the individual keys which constitute the keyboard and a novel mounting arrangement of the keys with respect to electrical components to be energized.
As used throughout the specification and the claims, the term keyboard is intended to include a grouping of key members or switches and the like on a panel which, when the key members are depressed or actuated, will cause another element such as a shaft to move which, in turn, actuates another device such as a mechanical or electrical component.
Many different groupings or arrays are made possible by utilizing individual key members and by positioning them in any desired configuration. For example so-called ten button key sets, alphanumeric displays, computer input terminals, typewriters, teletype machines, and telephone dials are only a few examples of typical keyboard constructions having different numbers and orientations of the individual keys. The mosaic-like feature of mounting and demounting independent separate keys and especially small-sized keys, to form a large array makes for a particularly economical and simple arrangement. In addition, repairs and/or interchangeability of the individual key members are greatly simplified.
One disadvantage of all prior art arrangements using push-type or locking-type keys, which is common to both electrical contact-type keys and so-called electrical contactless-type keys, is that the electrical switching operation occurs within the key member itself. Not only is solder necessary to make the electrical connection and other fastening means needed to secure the key members to a carrier, but also additional fasteners are needed to connect each key member with the electronic circuitry to be actuated.
A further disadvantage common to all of the aforementioned type key members is that such keys are generally only insertable and removable from a key-carrying member from beneath the latter. This limited accessibility is particularly disadvantageous when one desires to repair and/or interchange one of the individual keys with another.
One known prior-art arrangement utilizes clamping devices to securely fasten the keys and their carrying member to a printed circuit board support member. This arrangement also teaches using locking screws. Both the clamping device and the locking screws require, for their installation, relatively lengthy amounts of time, thus making repairs and/or interchange of components costly. Moreover, this arrangement is further disadvantageous since it teaches the use of solder connections with the electrical devices mounted on a circuit board. As noted above, such electrical connections must be desoldered before demounting the key members.
Another prior art arrangement teaches the insertion of keys from above to a recessed plate by means of a pair of diametrically opposite, elastic locking projections. However, as noted above, this prior art arrangement teaches the disadvantage that the electrical connections at the bottom of the keys must be secured to a printed circuit board by means of solder. Hence, quick demounting of keys from the plate is not possible. First of all, the solder connection securely holds the key member to the electric circuit board, and secondly, the pair of locking projections can only be secured together if one gains access to the region beneath the plate. Thus, specially-designed openings are required to be machined into the printed circuit board, and specially-designed tools which must fit into these specially-designed openings are required in order to engage the pair of locking projecrions. The only way that the keys can then be removed from the carrier is if the electrical connections have first been desoldered.
Still another prior art arrangement inserts the individual keys from above into a support plate. Moreover, the input and output electrical cables are not directly led to the individual key members. Collars are provided on the support plate to allow the actuating shafts of the key members to pass therethrough and to securely fasten each key member in position. However, such keys are prone to turning about their axes so that, in order to prevent such turning, side projections are additionally required to be provided on the cap of the key members. These caps are received in specially designed openings in the support plate. The cap, the return spring and the actuating shaft of each key member is installed through the collars from above, and then the actuating parts which actuate the electrical devices are moved from the underside of the support plate onto the shaft and connected together by means of a screw.
In short, this prior art arrangement requires that the support plate be accessible on both its upper and lower sides. If many keys are to be mounted on a support plate, the circuit board must be spaced from the support plate by a predetermined distance. To accomplish this, the prior art uses screws and shims. This arrangement is particularly disadvantageous since an interchange of the individual key members or else the circuit board itself is very difficult to accomplish, especially in a short period of time.
Another prior art mounting arrangement inserts individual keys in a support plate. A portion of each key projects through the support plate to the underside thereof and is held in position by means of locking screws. This mounting arrangement is particularly undesirable, because demounting an individual key is very difficult since the entire keyboard must be removed in order to loosen the particular screw associated with the key to be repaired.
Another known prior art arrangement mounts the keys on a plate having pins which are electrically connected to electrical devices to be energized. The keys themselves are held in their correct positions by rods so that a demounting for interchanging an individual key for another from the keyboard is not possible.